[linux-2.6-block.git] / include / uapi / linux / virtio_ring.h

#ifndef _UAPI_LINUX_VIRTIO_RING_H
#define _UAPI_LINUX_VIRTIO_RING_H
/* An interface for efficient virtio implementation, currently for use by KVM
 * and lguest, but hopefully others soon.  Do NOT change this since it will
 * break existing servers and clients.
 *
 * This header is BSD licensed so anyone can use the definitions to implement
 * compatible drivers/servers.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of IBM nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Copyright Rusty Russell IBM Corporation 2007. */
#include <linux/types.h>
#include <linux/virtio_types.h>

/* This marks a buffer as continuing via the next field. */
#define VRING_DESC_F_NEXT	1
/* This marks a buffer as write-only (otherwise read-only). */
#define VRING_DESC_F_WRITE	2
/* This means the buffer contains a list of buffer descriptors. */
#define VRING_DESC_F_INDIRECT	4

/* The Host uses this in used->flags to advise the Guest: don't kick me when
 * you add a buffer.  It's unreliable, so it's simply an optimization.  Guest
 * will still kick if it's out of buffers. */
#define VRING_USED_F_NO_NOTIFY	1
/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
 * when you consume a buffer.  It's unreliable, so it's simply an
 * optimization.  */
#define VRING_AVAIL_F_NO_INTERRUPT	1

/* We support indirect buffer descriptors */
#define VIRTIO_RING_F_INDIRECT_DESC	28

/* The Guest publishes the used index for which it expects an interrupt
 * at the end of the avail ring. Host should ignore the avail->flags field. */
/* The Host publishes the avail index for which it expects a kick
 * at the end of the used ring. Guest should ignore the used->flags field. */
#define VIRTIO_RING_F_EVENT_IDX		29

/* Virtio ring descriptors: 16 bytes.  These can chain together via "next". */
struct vring_desc {
	/* Address (guest-physical). */
	__virtio64 addr;
	/* Length. */
	__virtio32 len;
	/* The flags as indicated above. */
	__virtio16 flags;
	/* We chain unused descriptors via this, too */
	__virtio16 next;
};

struct vring_avail {
	__virtio16 flags;
	__virtio16 idx;
	__virtio16 ring[];
};

/* u32 is used here for ids for padding reasons. */
struct vring_used_elem {
	/* Index of start of used descriptor chain. */
	__virtio32 id;
	/* Total length of the descriptor chain which was used (written to) */
	__virtio32 len;
};

struct vring_used {
	__virtio16 flags;
	__virtio16 idx;
	struct vring_used_elem ring[];
};

struct vring {
	unsigned int num;

	struct vring_desc *desc;

	struct vring_avail *avail;

	struct vring_used *used;
};

/* Alignment requirements for vring elements.
 * When using pre-virtio 1.0 layout, these fall out naturally.
 */
#define VRING_AVAIL_ALIGN_SIZE 2
#define VRING_USED_ALIGN_SIZE 4
#define VRING_DESC_ALIGN_SIZE 16

/* The standard layout for the ring is a continuous chunk of memory which looks
 * like this.  We assume num is a power of 2.
 *
 * struct vring
 * {
 *	// The actual descriptors (16 bytes each)
 *	struct vring_desc desc[num];
 *
 *	// A ring of available descriptor heads with free-running index.
 *	__virtio16 avail_flags;
 *	__virtio16 avail_idx;
 *	__virtio16 available[num];
 *	__virtio16 used_event_idx;
 *
 *	// Padding to the next align boundary.
 *	char pad[];
 *
 *	// A ring of used descriptor heads with free-running index.
 *	__virtio16 used_flags;
 *	__virtio16 used_idx;
 *	struct vring_used_elem used[num];
 *	__virtio16 avail_event_idx;
 * };
 */
/* We publish the used event index at the end of the available ring, and vice
 * versa. They are at the end for backwards compatibility. */
#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
#define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])

static inline void vring_init(struct vring *vr, unsigned int num, void *p,
			      unsigned long align)
{
	vr->num = num;
	vr->desc = p;
	vr->avail = p + num*sizeof(struct vring_desc);
	vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(__virtio16)
		+ align-1) & ~(align - 1));
}

static inline unsigned vring_size(unsigned int num, unsigned long align)
{
	return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num)
		 + align - 1) & ~(align - 1))
		+ sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
}

/* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
/* Assuming a given event_idx value from the other side, if
 * we have just incremented index from old to new_idx,
 * should we trigger an event? */
static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
{
	/* Note: Xen has similar logic for notification hold-off
	 * in include/xen/interface/io/ring.h with req_event and req_prod
	 * corresponding to event_idx + 1 and new_idx respectively.
	 * Note also that req_event and req_prod in Xen start at 1,
	 * event indexes in virtio start at 0. */
	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
}

#endif /* _UAPI_LINUX_VIRTIO_RING_H */
Commit	Line	Data
607ca46e DH	1	#ifndef _UAPI_LINUX_VIRTIO_RING_H
	2	#define _UAPI_LINUX_VIRTIO_RING_H
	3	/* An interface for efficient virtio implementation, currently for use by KVM
	4	* and lguest, but hopefully others soon. Do NOT change this since it will
	5	* break existing servers and clients.
	6	*
	7	* This header is BSD licensed so anyone can use the definitions to implement
	8	* compatible drivers/servers.
	9	*
	10	* Redistribution and use in source and binary forms, with or without
	11	* modification, are permitted provided that the following conditions
	12	* are met:
	13	* 1. Redistributions of source code must retain the above copyright
	14	* notice, this list of conditions and the following disclaimer.
	15	* 2. Redistributions in binary form must reproduce the above copyright
	16	* notice, this list of conditions and the following disclaimer in the
	17	* documentation and/or other materials provided with the distribution.
	18	* 3. Neither the name of IBM nor the names of its contributors
	19	* may be used to endorse or promote products derived from this software
	20	* without specific prior written permission.
	21	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
	22	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	23	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	24	* ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
	25	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	26	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	27	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	28	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	29	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	30	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	31	* SUCH DAMAGE.
	32	*
	33	* Copyright Rusty Russell IBM Corporation 2007. */
	34	#include <linux/types.h>
eef960a0	35	#include <linux/virtio_types.h>
607ca46e DH	36
	37	/* This marks a buffer as continuing via the next field. */
	38	#define VRING_DESC_F_NEXT 1
	39	/* This marks a buffer as write-only (otherwise read-only). */
	40	#define VRING_DESC_F_WRITE 2
	41	/* This means the buffer contains a list of buffer descriptors. */
	42	#define VRING_DESC_F_INDIRECT 4
	43
	44	/* The Host uses this in used->flags to advise the Guest: don't kick me when
	45	* you add a buffer. It's unreliable, so it's simply an optimization. Guest
	46	* will still kick if it's out of buffers. */
	47	#define VRING_USED_F_NO_NOTIFY 1
	48	/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
	49	* when you consume a buffer. It's unreliable, so it's simply an
	50	* optimization. */
	51	#define VRING_AVAIL_F_NO_INTERRUPT 1
	52
	53	/* We support indirect buffer descriptors */
	54	#define VIRTIO_RING_F_INDIRECT_DESC 28
	55
	56	/* The Guest publishes the used index for which it expects an interrupt
	57	* at the end of the avail ring. Host should ignore the avail->flags field. */
	58	/* The Host publishes the avail index for which it expects a kick
	59	* at the end of the used ring. Guest should ignore the used->flags field. */
	60	#define VIRTIO_RING_F_EVENT_IDX 29
	61
	62	/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
	63	struct vring_desc {
	64	/* Address (guest-physical). */
eef960a0	65	__virtio64 addr;
607ca46e	66	/* Length. */
eef960a0	67	__virtio32 len;
607ca46e	68	/* The flags as indicated above. */
eef960a0	69	__virtio16 flags;
607ca46e	70	/* We chain unused descriptors via this, too */
eef960a0	71	__virtio16 next;
607ca46e DH	72	};
	73
	74	struct vring_avail {
eef960a0 MT	75	__virtio16 flags;
	76	__virtio16 idx;
	77	__virtio16 ring[];
607ca46e DH	78	};
	79
	80	/* u32 is used here for ids for padding reasons. */
	81	struct vring_used_elem {
	82	/* Index of start of used descriptor chain. */
eef960a0	83	__virtio32 id;
607ca46e	84	/* Total length of the descriptor chain which was used (written to) */
eef960a0	85	__virtio32 len;
607ca46e DH	86	};
	87
	88	struct vring_used {
eef960a0 MT	89	__virtio16 flags;
eef960a0 MT	90	__virtio16 idx;
607ca46e DH	91	struct vring_used_elem ring[];
	92	};
	93
	94	struct vring {
	95	unsigned int num;
	96
	97	struct vring_desc *desc;
	98
	99	struct vring_avail *avail;
	100
	101	struct vring_used *used;
	102	};
	103
b28e0506 MT	104	/* Alignment requirements for vring elements.
	105	* When using pre-virtio 1.0 layout, these fall out naturally.
	106	*/
	107	#define VRING_AVAIL_ALIGN_SIZE 2
	108	#define VRING_USED_ALIGN_SIZE 4
	109	#define VRING_DESC_ALIGN_SIZE 16
	110
607ca46e DH	111	/* The standard layout for the ring is a continuous chunk of memory which looks
	112	* like this. We assume num is a power of 2.
	113	*
	114	* struct vring
	115	* {
	116	* // The actual descriptors (16 bytes each)
	117	* struct vring_desc desc[num];
	118	*
	119	* // A ring of available descriptor heads with free-running index.
eef960a0 MT	120	* __virtio16 avail_flags;
	121	* __virtio16 avail_idx;
	122	* __virtio16 available[num];
	123	* __virtio16 used_event_idx;
607ca46e DH	124	*
	125	* // Padding to the next align boundary.
	126	* char pad[];
	127	*
	128	* // A ring of used descriptor heads with free-running index.
eef960a0 MT	129	* __virtio16 used_flags;
eef960a0 MT	130	* __virtio16 used_idx;
607ca46e	131	* struct vring_used_elem used[num];
eef960a0	132	* __virtio16 avail_event_idx;
607ca46e DH	133	* };
	134	*/
	135	/* We publish the used event index at the end of the available ring, and vice
	136	* versa. They are at the end for backwards compatibility. */
	137	#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
eef960a0	138	#define vring_avail_event(vr) ((__virtio16 )&(vr)->used->ring[(vr)->num])
607ca46e DH	139
	140	static inline void vring_init(struct vring vr, unsigned int num, void p,
	141	unsigned long align)
	142	{
	143	vr->num = num;
	144	vr->desc = p;
	145	vr->avail = p + num*sizeof(struct vring_desc);
eef960a0	146	vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(__virtio16)
607ca46e DH	147	+ align-1) & ~(align - 1));
	148	}
	149
	150	static inline unsigned vring_size(unsigned int num, unsigned long align)
	151	{
eef960a0	152	return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num)
607ca46e	153	+ align - 1) & ~(align - 1))
eef960a0	154	+ sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
607ca46e DH	155	}
	156
	157	/* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
e412d3a3	158	/* Assuming a given event_idx value from the other side, if
607ca46e DH	159	* we have just incremented index from old to new_idx,
	160	* should we trigger an event? */
	161	static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
	162	{
	163	/* Note: Xen has similar logic for notification hold-off
	164	* in include/xen/interface/io/ring.h with req_event and req_prod
	165	* corresponding to event_idx + 1 and new_idx respectively.
	166	* Note also that req_event and req_prod in Xen start at 1,
	167	* event indexes in virtio start at 0. */
	168	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
	169	}
	170
	171	#endif /* _UAPI_LINUX_VIRTIO_RING_H */